1. Field of the Invention
The present invention relates to an electroconductive polymer composition, an electroconductive polymer material, an electroconductive substrate, an electrode and a solid electrolytic capacitor.
2. Description of the Related Art
Electroconductive organic materials are utilized as an antistatic material or an electromagnetic shielding material as well as for electrodes of capacitors, electrochemical capacitors or the like, for electrodes of dye-sensitized solar cells, organic film solar cells or the like, for electrodes of electroluminescence displays, or the like.
As the electroconductive organic material, electroconductive polymers obtained by polymerizing pyrrole, thiophene, 3,4-ethylenedioxythiophene, aniline or the like are known. These electroconductive polymers are generally provided in a state of a dispersion liquid or a solution in an aqueous solvent, or in a state of a solvent in an organic solvent, and are used as an electroconductive polymer material after the solvent is removed.
Recently, an electroconductive polymer material with a higher electroconductivity is required, and it is variously studied. JP 2004-59666 A discloses a technology regarding an aqueous dispersion of a composite of a poly(3,4-dialkoxythiophene) with a polyanion and a method for producing the same, as well as a coating composition containing the aqueous dispersion and a coated substrate having a transparent electroconductive film to which the composition are applied. It is disclosed that a water-soluble compound having an amide bond, a water-soluble sulfoxide or the like is added to an aqueous dispersion of a composite of poly(3,4-dialkoxythiophene) with a polyanion in order to improve the electroconductivity of the coating film.
JP 2005-123630 A discloses a technology regarding a solid electrolyte produced from an electroconductive polymer, an electrolytic capacitor with a low equivalent series resistance and a low leakage current which consists of an outer layer containing an electroconductive polymer and a polymer anion, and a method for producing the same. It is disclosed that an additive such as an ether group-containing compound, a lactone group-containing compound, an amide or lactam group-containing compound, a sulfone or a sulfoxide, a sugar or a sugar derivative, a sugar alcohol, a furan derivative, or a polyalcohol is contained in order to further improve the electroconductivity of the electroconductive polymer.
JP 2000-153229 A discloses a thin film with a high electroconductivity which is obtained by applying a coating composition containing a non-protic chemical compound with dielectric constant ∈ of 15 or more to a substrate and by drying it at a temperature lower than 100° C.
However, to these electroconductive organic materials, not only high electroconductivity and high transparency but also good film forming property of the electroconductive film to the substrate to the substrate is required as an essential factor in order to actually use it as an electrode. The good film forming property means a state that a shrinkage, a crack, a wrinkle and foam of the film are not generated when the solution is applied and dried. Also, as a result, the electroconductive film with such good film forming property often has a high electroconductivity, a high transparency and a good adhesion to the substrate.
As a method for improving the film forming property, a method by adding an additive (solid or liquid), a resin (binder), a surfactant or the like is generally known. However, if this is mixed, the dispersion state of the electroconductive polymer composition is often deteriorated and a good film forming property is not obtained.
JP 2004-59666 A, JP 2005-123630 A and JP 2000-153229 A disclose that the electroconductivity is improved by adding an additive to an electroconductive polymer composition in which a polyanion is doped. On the other hand, these do not at all disclose the dispersion state and the film forming property of the electroconductive polymer composition. If an additive suitable for a component of the electroconductive polymer is not used, the dispersion state of the electroconductive polymer is deteriorated, and the increase of the viscosity and the particle diameter occurs due to the aggregation. As a result, the film forming property of the electroconductive polymer composition is deteriorated, and a shrinkage, a crack, a wrinkle and foam of the film are generated. Also, the transparency of the electroconductive film is deteriorated due to the increase of the particle diameter.
The object of the present invention is to provide an electroconductive polymer composition with a good film forming property. Also, the object of the present invention is to provide an electroconductive polymer material with a high electroconductivity and a high transparency as well as an electroconductive substrate having the electroconductive polymer material on a substrate, and an electrode. Further, the object of the present invention is to provide an electronic device having the electrode as well as a solid electrolytic capacitor with a high capacitance and a low ESR.